1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to transmitting and/or receiving digital content, and more particularly, to a device on a home network which uses digital content provided from a content server.
2. Description of the Related Art
With rapid development of wired and wireless communication technologies based on transmission control protocol/Internet protocol (TCP/IP), transmission and reception of digital content through TCP/IP wired and wireless networks have been increasingly performed. Since the transmission and reception of digital content through wired and wireless networks are performed between two devices separated a remote distance from each other, the communication is exposed to a security risk. A security risk, in terms of a device unauthorized to transmit or receive digital content, such as hacking or eavesdropping, always exists. Since the content transmitted and received through wired and wireless networks is digital, and thus is easily copied, this security risk is more critical to the copyright management of the digital content.
One security method used to handle this security risk is a conditional access system (CAS). The CAS is a system giving authority to access fee-paying digital content, or restricting access to the digital content. The digital content, which a content server encrypts and transmits, can be decrypted by using an encryption key only when a reception device has a right to access digital content. By allowing the reception device to use the content only when the reception device is permitted to access the content by paying the fee to use the content, unauthorized duplication of the digital content is prevented. A method of transmitting and receiving digital content by using the CAS will now be explained in relation to an example of an Internet protocol television (IPTV).
FIG. 1 is a diagram illustrating a conventional method of transmitting and receiving digital content. FIG. 1 illustrates the method which has been recently suggested in order for a plurality of devices in a home network to transmit and receive digital content provided through an IPTV network.
Referring to FIG. 1, an IPTV set-top box 12 receives digital content and information on the content provided by a content server 11, converts the content into a form that can be provided through a home network, and transmits the converted content to TV 1 13 through TV 3 15. The information on the content may include metadata, electronic program guide (EPG) information, and video on demand (VOD) list information of the content.
The IPTV set-top box 12 which receives the content and information on the content from the content server 11, first, converts the information on the content into a form that can be provided through the home network, and discloses the converted information to TV 1 13 through TV 3 15. For example, according to a method of updating the list of a content directory service (CDS) of a universal plug and play (UPnP) network based on the information on the received convent, the information on the content can be disclosed to devices in the home network.
TV1 13 through TV 3 15 request the IPTV set-top box 12 to transmit predetermined digital content based on the information on the content. The IPTV set-top box 12 requests the content server 11 to provide the content requested by TV1 13 through TV3 15, and receives the content encrypted with a predetermined encryption key. Since the content server 11 and the IPTV set-top box 12 control access by using the CAS, only the IPTV set-top box 12 can decrypt the content transmitted by the content server 11, by using the key used for the encryption. Both symmetric keys and asymmetric keys can be used as the encryption key.
The IPTV set-top box 12 decrypts the received content, and transmits the content to TV1 13 through TV3 15. When the IPTV set-top box 12 relays the received content to TV1 13 through TV3 15, the IPTV set-top box 12 encrypts the content received from the content server 11, with a predetermined encryption key, and transmits the content. Even in the home network formed with the IPTV set-top box 12 and the TVs, it is necessary to restrict access to the content by devices that do not have a right to receive the content. Accordingly, the IPTV set-top box 12 encrypts the content by using the encryption key and transmits the encrypted content.
When the IPTV set-top box 12 encrypts the content, a security method used when the content is transmitted and received in the home network is used. Accordingly, in the home network, a method unique to the network is used to register and/or authenticate a device at the other end, and the encrypted content is transmitted to only registered and authenticated devices. The encryption key used in the home network is different from the encryption key used by the content server when the content is encrypted, and the method of exchanging and managing the encryption key is also different to the method used by the content server 11.
When the IPTV set-top box 12 transmits the content to one device, that is, one of TV1 13 through TV3 15, the content is transmitted according to the method described above. However, when the IPTV set-top box 12 transmits the content to a plurality of devices from among TV1 13 through TV3 15 at the same time, an overload may occur in the IPTV set-top box 12.
As described above, the IPTV set-top box 12 decrypts the content transmitted by the content server 11, encrypts the content again and transmits the content to a device in the home network. In this case, for the encryption and decryption, a data encryption standard (DES), an advancement encryption standard (AES), or a T-DES that is a standardized symmetric key method is used. The low-priced IPTV set-top box 12 that is provided as a hardware module for encryption and decryption can perform encryption and decryption of only one digital content file at a time. That is, when the content to be provided to TV1 13 is decrypted and encrypted, another content file cannot be transmitted to TV2 14 or TV3 15.
Accordingly, a method of embedding an IPTV set-top box 12 in each of the devices 13 through 15 on the home network can be considered. However, in this case, all the devices become set-top boxes, which is not efficient in terms of cost.
Also, in order to manage copyrights of IPTV content files more effectively, a predetermined copy protection technology should be applied to the IPTV set-top box 12 and the devices 13 through 15 in the home network. This increases complexity of the devices 13 through 15 on the home network and increases manufacturing costs.
Accordingly, a method capable of guaranteeing security of transmission and reception of digital content and efficiently relaying digital content is desired.